In the past, sun screens, foundations, etc. have been known as cosmetic compositions for preventing sunburn. In these cosmetic compositions UV absorbents and UV blocking agents are formulated as substances for blocking UV rays. In these, fine particles of titanium dioxide having an average particle size of 0.03 to 0.05 .mu.m have been generally used as UV blocking agents. The applicant of the present invention previously obtained a cosmetic composition having a high UV protective effect by formulating a combination of spherical fine particles of titanium dioxide having an average particle size of 0.01 to 0.10 .mu.m and needle type (spindle shaped) fine particles of titanium dioxide having a short diameter of 0.005 to 0.02 .mu.m and a long diameter of 0.01 to 0.10 .mu.m (Japanese Patent Application No. 5-340571 (i.e., JP-A-7-165532)).
However, these fine particles of titanium dioxide are hard to disperse in the single particle state in a cosmetic composition since the particle size is small. Therefore, in actuality, they exist as considerably large aggregates. Further, when metal oxides having a large relative particle size are formulated in a cosmetic composition, the metal oxides form the nucleus for easy formation of aggregates and the effect for preventing UV rays inherently exhibited remarkably falls. In particular, in a solid foundation, since the components are a powder and oil in a paste composition, the fine particles of powder easily aggregate as nuclei the relatively large particle size powder. The above trend becomes particularly conspicuous. Accordingly, even if fine particles of titanium dioxide are formulated in the cosmetic composition, it is hard to obtain the desired UV protecting effect. Even if the amount of formulation is increased, the effect for protecting the UV rays will not rise, the feeling to the skin will become poorer, the finish will become powdery, and other defects will appear.
Further, fine particles of titanium dioxide have the effect for blocking UVB of the region of 290 nm to 320 nm, but are insufficient in the effect for blocking UVA having a region of 320 nm to 400 nm, and therefore, have had the defect of not being able to prevent skin disorders due to UVA--which have recently been taken up as an issue.